Allow a delete duration of 0.

This change covers the case where a reply is requested.  A separate,
more complicated change mixes in noreplys and 0 duration deletes.

memcached.c

@@ -2883,7 +2883,8 @@ static void process_delete_command(conn *c, token_t *tokens, const size_t ntoken
     assert(c != NULL);
 
     if (ntokens == 4) {
-        if (!set_noreply_maybe(c, tokens, ntokens)) {
+        if (strcmp(tokens[KEY_TOKEN+1].value, "0") != 0
+            && !set_noreply_maybe(c, tokens, ntokens)) {
             out_string(c, "CLIENT_ERROR bad command line format.  "
                        "Usage: delete <key> [noreply]");
             return;

t/issue_108.t

@@ -0,0 +1,20 @@
+#!/usr/bin/perl
+
+use strict;
+use Test::More tests => 3;
+use FindBin qw($Bin);
+use lib "$Bin/lib";
+use MemcachedTest;
+
+my $server = new_memcached();
+my $sock = $server->sock;
+my $key = "del_key";
+
+print $sock "add $key 0 0 1\r\nx\r\n";
+is (scalar <$sock>, "STORED\r\n", "Added a key");
+
+print $sock "delete $key 0\r\n";
+is (scalar <$sock>, "DELETED\r\n", "Properly deleted with 0");
+
+print $sock "add $key 0 0 1\r\nx\r\n";
+is (scalar <$sock>, "STORED\r\n", "Added again a key");